1. Field of the Invention
The invention relates generally to induction motors. In particular, the invention relates to multi-speed, pole-changing, single phase induction motors having a partially shared winding configuration.
2. Description of the Prior Art
Single phase induction motors (including capacitor start motors and split phase motors) having two or more pole configurations are useful in many multi-speed motor applications. For example, some washing machines employ 4/6/8 pole single phase induction motors because such motors provide multi-speed operation for various cycles within a certain speed range, and without the need for additional complicated and expensive controls such as a variable frequency controller. There is a continuing need to design such motors to provide good performance for both running and starting at a low cost of materials and manufacture. The running performance includes evaluating such factors as torque, speed, current, temperature rise, efficiency, size and other factors. The starting performance includes evaluation of the speed-torque curves of the motor.
Some 4/6/8 pole motors in production employ basically independent 4-pole, 6-pole, and 8-pole main windings, as well as an auxiliary winding (e.g a 4-pole auxiliary winding) for starting. In some prior art configurations, the 6-pole winding shares a portion of the 4-pole winding. To reduce the size of the motor and save active material, a new approach to sharing the 4-pole and 8-pole windings has been developed and is described in a co-invented and co-assigned PCT patent application Ser. No. PCT/US99/11235, filed May 20, 1999, entitled SINGLE PHASE THREE SPEED MOTOR WITH SHARED WINDINGS (International Publication Number WO 99/63645), the entire disclosure of which is incorporated herein by reference. In particular, the fully-shared 4/8 pole configuration illustrated therein employs a winding configuration in which all of the windings energized for operating in the 8-pole mode are also energized for operating in the 4-pole mode, no separate winding is provided to operate in the 8-pole mode.
One advantage of the fully shared winding approach is that it reduces manufacturing costs by reducing the amount of wire needed and/or by reducing the stator size. On the other hand, to reconnect the main winding from a 4-pole configuration to an 8-pole configuration, or visa versa, one more contact (such as a single pole, single throw switch) is needed either as part of a starting switch or as part of an external circuit of the motor. If the additional contact is implemented as part of the starting switch, the starting switch will require three switches and four contacts. This implementation makes the starting switch more complicated and expensive to retool and produce. On the other hand, if the additional contact is implemented as part of the external circuit of the motor, the additional contact would typically be in the form of a timer or a relay.
In either case, a new contact is needed to take advantage of the fully shared winding approach. In many circumstances, providing a new contact is an acceptable consideration. In some circumstances, however, a new contact is not desirable. For example, adding a new contact to an existing appliance configuration may be impracticable. As a specific example, adding a new contact does not allow the above described 4/8 pole fully shared motor configuration to be used as a drop in replacement for an existing motor in an appliance configuration that does not provide the additional contact.
For these reasons, a new partially shared winding motor configuration is desired. Such a partially shared winding motor configuration benefits from reduced wiring requirements while eliminating the need for an additional contact. In one form, a partially shared winding motor configuration is chosen to provide a form, fit, and function replacement for an existing appliance motor, without requiring any new contacts.
The invention meets the above needs and overcomes the deficiencies of the prior art by providing an improved multi-speed induction motor. Briefly described, a single phase, multi-speed induction motor embodying aspects of the invention includes a stator core. A rotor is mounted in a rotational relationship with the stator core. A partially shared winding is on the stator core. The partially shared winding is energized in its entirety when it is desirable to operate the motor in a 4-pole configuration. The partially shared winding is energized in less than its entirety when it is desirable to operate the motor in an 8-pole configuration.
Another embodiment of a motor embodying aspects of the invention includes a stator core. A rotor is mounted in a rotational relationship with the stator core. A plurality of winding components are wound on the stator core. A first one of the plurality of winding components and a second one of the plurality of winding components are selectively energized to operate the motor at a 4-pole pole speed. A third one of the plurality of winding components and the first one of the plurality of winding components are selectively energized to operate the motor at an 8-pole pole speed such that the second one of the plurality of winding components is only energized when the motor is operated at the 4-pole pole speed.
In another aspect, the invention relates to a single phase, three-speed induction motor. The motor includes a stator core and a rotor in rotational relationship with the stator core. A first winding is wound on the stator core and is selectively energized in an N-pole configuration. N is at least two and is an integer multiple of two. The first winding includes a first winding portion and a second winding portion. A second winding is wound on the stator core and is selectively energized in an M-pole configuration. M is two-times N. The second winding shares the first winding portion of the first winding but not the second winding portion of the first winding.
In still another aspect, the invention relates to a motor that is arranged to be operated at a plurality of pole speeds. The motor includes a stator core and a rotor in rotational relationship with the stator core. A first winding portion is on the stator core for operating the motor at a first pole speed. The first winding portion has a substantially sinusoidal wire turn distribution. A second winding portion is on the stator core for operating the motor at the first pole speed. The second winding portion has a substantially nonsinusoidal wire turn distribution.
In yet another aspect, the invention relates to a motor arranged to be operated in a 4-pole configuration and in an 8-pole configuration. The motor includes a stator core and a rotor in rotational relationship with the stator core. A first winding portion is wound on the stator core and is energized only when operating the motor in the 4-pole configuration. The first winding portion has a substantially sinusoidal wire distribution. A second winding portion is wound on the stator core and energized when operating the motor in the 4-pole configuration and the 8-pole configuration. The second winding portion has a substantially nonsinusoidal wire distribution.
In another aspect, the invention relates to a motor arranged to be operated in a 4-pole configuration, a 6-pole configuration, and an 8-pole configuration. The motor includes a stator core and a rotor in rotational relationship with the stator core. A first winding portion is wound on the stator core and is energized in the 4-pole configuration only. A second winding portion is wound on the stator core and is energized in the 6-pole configuration only. A third winding portion is wound on the stator core and is energized in the 8-pole configuration only. A fourth winding portion is wound on the stator core and is energized in the 4-pole configuration and the 8-pole configuration, but is not energized in the 6-pole configuration.
In another aspect, the invention relates to methods of manufacturing, including methods of manufacturing induction motors and stators for use in connection with induction motors. Such methods include: providing a 4-pole winding that is partially shared in an 8-pole winding configuration; providing a winding that includes a sinusoidally wound winding portion and a non-sinusoidally wound winding portion; and/or providing a winding that includes winding portions that are placed in the slots about the stator in a non-sequential crisscross pattern.
Alternatively, the invention may comprise various other devices, methods, and systems.
Other objects and features will be in part apparent and in part pointed out hereinafter.